The overall purpose of the proposed studies is to compare the structure- activity relationships of the subjective effects of delta-9- tetrahydrocannabinol (delta-9-THC) and other cannabimimetics with an analog (R-methanandamide) of the endogenous cannabinoid receptor ligand anandamide. The SAR between chemical structure and drug action reveals the structural requirements for a given drug effect or drug action. Though some studies suggest that delta-9-THC and anandamide as well as R-methanandamide share many similar properties, a one-on-one relationship has not been demonstrated. Studies from our own and other laboratories have shown the THC-like properties of synthetic cannabinoids and cannabimimetics are highly dependent on particular structural configurations. The proposed studies investigate potential stereoselectivity of known cannabimimetic compounds with regard to R- methanandamide. These studies also focus on identifying useful pharmacotherapies for cannabis abuse by effectively blocking the psychoactive, cannabimimetic properties. The present project will utilize drug discrimination procedures with rats as an animal model for assessing the psychoactive properties of delta-9-THC, R-methanandamide, and related compounds. Drug discrimination is the most commonly used paradigm for studying the subjective, intoxicating effects of drugs in preclinical psychopharmacology. A special feature of this proposal is the use of different training doses of THC to create different efficacy demands. Additionally, food maintained responding and open-field activity studies will also be conducted. By providing important information on the SAR of endogenous anandamide and exogenous delta-9- THC, as well as potential cannabimimetic antagonists, these studies will not only add to our understanding of the behavioral neurobiology of cannabis abuse and dependence, but may also lead to the development of effective pharmacological treatments.